This is the blog for Yale's undergrad course ANTH204:
An introduction to the patterns and processes of human genetic variation. Topics include: human origins and migration; molecular adaptations to environment, lifestyle and disease; ancient and forensic DNA analyses; and genealogical reconstructions.

Wednesday, September 21, 2011

Glowing Kittens Fight Feline AIDS

The world is generally aware of the AIDS epidemic. While HIV is a commonly recognized infectious virus, there are actually two AIDS epidemics worldwide. One is human immunodeficiency virus (HIV); the other AIDS epidemic is feline immunodeficiency virus (FIV) found in your common housecat, of which there are 90 million in the United States alone. Known as lentiviruses, FIV and HIV produce similar symptoms but are non-transmittable between felines and humans. Why?

In 2007, scientists at the Laboratory of Genomic Diversity finished the Cat Genome Project. Using this data to the human genome, scientists in previous studies have hypothesized that the issue was the cat’s lack of the antiretroviral restriction factor protein TRIMCyp generated by the TRIM5 gene. Possessed by humans and monkeys, the gene codes for proteins that target the outer-shell of the FIV virus, marking it for degradation. Lacking this protein, felines are far more susceptible to FIV.

Would a feline with the TRIMCyp generesist FIV? Molecular virologist Eric Poeschlahypothesized yes; however, the intentional insertion of new genetic material into an embryo is difficult. Somatic cell nuclear transfer -- replacing the egg nucleus with that of an adult with the new genetic material -- only has a 3% chance of success. Instead, Poeschla turned to a virus. For the first time using a carnivore subject, he and his team created a new lentiviruscontaining both the gene TRIMCyp, but also a green fluorescent protein (GFP) commonly found in jellyfish. Infected with the virus and fertilized by regular cat sperm, eggs were placed into the fallopian tubes of 22 cats. The result was three kittens. This embryonic version of gene modification, with 23% efficiency, was significantly better than the previous 3% efficient procedure.

Thanks to GFP, scientists did not have to run tests or examine the offspring’s DNA to determine whether the new genetic material had successfully transferred. Scientists only had to turn off the lights, shine a blue light, and look for the green, glowing cat. And back in the laboratory, FIV replicated poorly in the bloods cells of the genetically modified kittens.

Implications of this gene therapy experiment are still unclear. While the kittens are not cured or immune to FIV, the experiment ultimately demonstrates potential factors to the process of gene therapy. Obviously, the human genome most likely will not be altered to include the green fluorescent protein. Nor will we be able to buy green, glowing cats at PetCo. But, this form of embryonic gene therapy, with a higher efficiency rate than the previous proven method, suggests a potential for future human gene therapy. And if the HIV virus can be manipulated in manner similar to FIV, the benefits for humans are even more obvious.